The present invention relates generally to antennas and transmission lines, and more particularly, to a continuous transverse stub disposed on one or both conductive plates of a parallel-plate waveguide, and antenna arrays, filters and couplers made therefrom.
At microwave frequencies, it is conventional to use slotted waveguide arrays, printed patch arrays, and reflector and lens systems. However, as the frequencies in use increase to 20 GHz and above, it becomes more difficult to use these conventional microwave elements.
The present invention relates to devices useful at frequencies as high as 20 GHz and up known as millimeter-wave and quasi-optical frequencies. Such devices take on a nature similar to strip line, microstrip or plastic antenna arrays or transmission lines. Such devices are fabricated in much the same way as optical fibers are fabricated.
Conventional slotted planar array antennas are difficult to use above 20 GHz because of their complicated design. This, in conjunction with the precision and complexity required in the machining, joining, and assembly of such antennas, further limits their use.
Printed patch array antennas suffer from inferior efficiency due to their high dissipative losses, particularly at higher frequencies and for larger arrays. Frequency bandwidths for such antennas are typically less than that which can be realized with slotted planar arrays. Sensitivity to dimensional and material tolerances is greater in this type of array due to the dielectric loading and resonant structures inherent in their design.
Reflector and lens antennas are generally employed in applications for which planar array antennas are undesirable, and for which the additional bulk and weight of a reflector or lens system is deemed to be acceptable. The absence of discrete aperture excitation control in traditional reflector and lens antennas limit their effectiveness in low sidelobe and shaped-beam applications.
Filters at millimeter-wave and quasi-optical frequencies suffer from relatively low Q-factors due to high dissipative element and interconnect losses and from relative difficulty in fabrication due to dimensional tolerances.